1. Technical Field
The invention relates to a flanged bush, in particular a flanged bush for plain bearings with at least one flange formed thereon, and to, a method for the production thereof and a bending die.
2. Related Art
Flanged bushes, which comprise either one or two flanges, are known in a very wide range of sizes, with diameters ranging from centimeters to decimeters. The materials used depend on the intended application, wherein the bush material may be of single- or multilayer construction. Single-layer bushes are known as solid bushes. Bushes of multilayer construction generally comprise a backing material and an overlay. The overlay may consist of a metal alloy or plastics. The invention relates to all flanged bushes, irrespective of their dimensions, intended purpose and the materials used, with the one reservation that the flanged bushes have to comprise at least one metallic layer.
To produce flanged bushes, an edge of prefabricated bearing sleeves or bushes is bent into a flange in a secondary operation. A conventional method is bush wrapping, wherein a flat strip portion, the so-called blank, is wrapped round to form a bush or sleeve.
In the case of wrapped bearing bushes, it is generally necessary for the butt joint to be closed when the bush is fitted, while the butt joint is generally not fully closed when the bearing bush is not fitted, since the material springs open to a greater or lesser degree depending on the method used to produce the bush 9c.f. DIN 1494, part 1, June 1983, p. 1).
Production methods for wrapped bushes are known and are described for example by Dipl.-Ing. Hugo Kotthaus in ‘Betriebstechnisches Taschenbush”, vol. 2, 7th edition, Karl Hanser Verlag Munich, 1967, pp. 212ff.
To close open butt joints, it is proposed in DE-OS 23 17 564 to heat the bushes and simultaneously to prevent an increase in diameter as a result of thermal expansion.
Both with this known method and with a shaping method described in DE-PS 517530, is it possible to close the butt gap in bushes.
However, if such prefabricated bushes are shaped into flanged bushes, by bending the edge of the bush, the butt joint opens up again, wherein the gap width may assume considerable dimensions depending on the diameter and flange width.
Flanged bushes with gaps can only be fitted using special tools, with which the flanged bush is compressed through the application of considerable force, wherein the flanged bush may possibly also warp, causing damage to the flanged bush.
Relatively small flanged bushes, which are transported in large numbers in cartons as loose cargo, may become hooked together, often resulting in a chain of several flanged bushes. The buyer has to separate the flanged bushes laboriously and generally by hand before fitting them. There has therefore long been a desire for flanged bushes with closed butt joints.
In flanged bushes, a closed butt joint could only be achieved by welding a ring forming the flange to a bush. The disadvantage of this method is that welding is more expensive than bending of the bush edge.